Bend-stretch apparatus for testing formable material

ABSTRACT

A device for testing the effect of forming forces on the surface of or on a coating applied to a formable material, the device including two spaced-apart means for clamping the material, and a radius corner means located in a fixed position between the two clamping means in substantial alignment therewith. On each side of the corner means is disposed a structure providing cam surfaces located in a fixed radial relationship to the corner means. At least one of the clamping means is provided with cam following means disposed to engage the cam surfaces. When the movable clamping means is moved along the extent of the cam surfaces, with a test piece of the formable material tightly clamped between the clamping means, the test piece is bent and elongated in the manner encountered in a forming operation in which the material undergoes a substantial amount of stretching while being subjected to a substantial bend.

United States Patent [151 3,636,758 McKee et al. 51 Jan. 25, 1972 [54] BEND STRETCH APPARATUS FOR 50,136 3/1969 Germany ..73/ 100 892,354 4/1944 France ..73/l00 [72] Inventors: Francis G. McKee, New Kensington; Roger C. Haddon, Monroeville, both of Pa.

[73] Assignee: Aluminum Company of America, Pittsburgh, Pa.

[22] Filed: Apr. 20, 1970 [21] Appl.No.: 29,835

[52] U.S.Ci ..73/l00,73/103 [51] Int.Cl. ..G0ln3/20 [58] FieldofSearch ..73/100,95,93;72/30l,302, 72/309-311, 298, 378

[56] References Cited UNITED STATES PATENTS 2,824,594 2/1958 Gray 153/48 2,496,029 1/1950 White,Jr.etal.. .....73/93 2,007,286 7/1935 Schopper ..73/51 2,462,826 2/1949 Waard eta]. 73/100 2,473,841 6/1949 Anderson ..73/i00 FOREIGN PATENTS OR APPLICATIONS 756,790 9/1956 GreatlBritain ..73/l00 TESTING FORMABLE MATERIAL Primary Examiner-Richard C. Queisser Assistant Examiner-John Whalen Attorney-Biro)! Strickland 5 7] ABSTRACT A device for testing the effect of forming forces on the surface of or on a coating applied to a formable material, the device including two spaced-apart means for clamping the material, and a radius corner means located in a fixed position between the two clamping means in substantial alignment therewith. On each side of the corner means is disposed a structure providing cam surfaces located in a fixed radial relationship to the corner means. At least one of the clamping means is provided with cam following means disposed to engage the cam surfaces. When the movable clamping means is moved along the extent of the cam surfaces, with a test piece of the formable material tightly clamped between the clamping means, the test piece is bent and elongated in the manner encountered in a forming operation in which the material undergoes a substantial amount of stretching while being subjected to a substantial bend.

BEND-STRETCH APPARATUS FOR TESTING FORMABLE MATERIAL BACKGROUND OF THE INVENTION The present invention relates generally to apparatus for bending and stretching a formable piece of material, and particularly to a device capable of simulating the bending and stretching conditions encountered by a metal material when it is formed and shaped in a process involving a substantial amount of elongation and bending.

When a material, sheet metal for example, is formed into a desired shape or configuration by simply bending over a comer means without gripping two opposed ends of the material, the outside of the bend is stretched, the amount of stretch being dependent on bend radii and material thickness. This type of bending is common in metal working and is not of interest to this disclosure.

There are, however, many metal-working processes, e.g., roll forming, where material is clamped during forming operations either intentionally or by virtue of the shape of the part being formed, for example, the curved configurations of rollformed aluminum siding. If the material being formed is coated, the coating on the outside of a bend can be subjected to a substantial stretch and elongation. The ability of the coating to bend and stretch, however, is often not as great as that of the base material so that during the forming operation the coating may deteriorate in the area of the bend, e.g., crack or craze, while the base material remains in good condition. The deterioration can usually be detected by visual inspection of the coated surface.

When a formable material is clamped during a bending operation, the surface of the material on the outside of the bend is subjected to stretching over and above that encountered in free bending. With surface stretching, conditions are encountered which enhance the formation of such known defects as orange peel, leuders lines, and roping or looper lines. Such defects are highly undesirable when the formed product of the material is uncoated and is required to have an aesthetically pleasing appearance and a smooth surface, for example, as needed for trim components in the automobile industry. In such cases, the peel or lines must be removed, by extensive buffing, for example, which adds considerable cost to the formed product. While there are various tests that provide the result of either stretching or bending forces in the formation of these defects, there are no testing devices and methods at present that demonstrate the effect of both forces occurring simultaneously.

Miscellaneous devices for testing the quality of a coating on a base material have been developed and used, but these devices have not provided the type of test in which the bending and elongating forces encountered in forming operations, which bend and stretch the coated material with substantial severity, can be accurately simulated.

To proceed with the forming operation, in which substantial amounts of coated r uncoated material may be involved, without knowing the effects of the bending and stretching forces on the material or coating, can be quite costly if the material surface or coating does, in fact, show defects as a result of such forces. What is therefore needed is a device for testing a sample or specimen of the material in a manner that will simulate the stringent conditions encountered in the type of forming processes which bend and elongate the material in amounts in excess of that encountered in a simple bending operation.

BRIEF SUMMARY OF THE INVENTION The present invention provides such a test device, the device being economical to make and simple to use. More particularly, the device comprises two clamping means respectively disposed on two sides of a radius corner means and in substantial alignment therewith. At least one of the clamping means is mounted to move along the surfaces of cam structures providing a predetermined, increasing radius about the comer means. To test the formability of a coating on a base material, a strip of the coated material is tightly clamped by the clamping means, and the movable clamping means then moved along the cam surfaces to bend and stretch the material over the comer means, the amount of the bend and stretch being essentially that encountered in a forming operation in which the material will undergo a substantial amount of bending and elongation.

The device, as briefly described, can further be employed to test the effect of bending and stretching on the surface condition of uncoated material. The device, for example, can be used to test for the above-mentioned surface conditions of orange peel, leuders lines and roping. Roping occurs when certain metals and alloys are formed in such a manner that the forming forces impose tension to the material in a direction other than the direction in which the metal was originally worked or rolled.

By use of changeable cams and radius corners, the amount of stretch and the severity of the bend can be altered to simulate different forming operations and conditions. In this manner, a flexible, quality control device is provided that has heretofore been unavailable in the art in which formable materials have been formed by a substantial amount of bending and stretching.

THE DRAWINGS The invention, along with its objectives and advantages, will be more apparent upon consideration of the following detailed description taken in connection with the accompanying drawings in which:

FIG. I is a side elevation view of a test device constructed in accordance with principles of the invention; and

FIG. 2 is a front elevation view of the device shown in FIG. 1.

PREFERRED EMBODIMENT Specifically, FIG. 1 shows a side elevation view of device or apparatus 10 for testing the surface condition of formable material, for examples, aluminum sheet, either coated or uncoated, though the invention is not limited to testing only aluminum sheet.

The device 10 comprises basically two clamping assemblies, generally designated l2 and 14, located respectively below and above a fixed radius comer means 16, and two fixed, vertically disposed plate structures 18 and 20 (FIG. 2) providing curved cam surfaces 22 and 24 respectively. As shown in the figures, the plate structures are substantially larger than the comer means 16, and are positioned in relation thereto to locate the cam surfaces externally of and at predetermined distance from the corner means. A baseplate 25 is provided to support these stnrctures in a manner to form an integral, unitary device as explained in more detail hereinafter.

The clamping assemblies 12 and 14, as depicted in the figures, are well known overcenter clamps in which a movable jaw 26, referring to the lower clamping assembly, is moved in relationship to a fixed jaw 27 by a lever arm 28. The upper clamping assembly 14 has corresponding jaws 29 and 30 and a lever arm 31. The arms are pivoted in a manner to move the jaws 26 and 29 into tight engagement with the fixed jaws 27 and 30 when the lever arm is disposed in an overcenter clamping position, and to move the jaws 26 and 29 away from the jaws 27 and 30 when the arms are disposed in a second, relaxed overcenter position. In the figures, the lever arms 28 and 31 are shown in the relaxed overcenter position. As shown in FIG. 1, each of the jaws may be provided with a serrated or otherwise roughened, inwardly facing surfaces 32.

The fixed jaw 27, as shown in FIG. 1, is a part of a support block 33 suitably attached to the baseplate 25, for example, by bolts 334 shown in phantom in FIG. I. Spaced to the left of the fixed jaw (in FIG. I) is a yoke structure 34 suitable for supporting the lever arm 28 and the movable jaw 26, the yoke structure being similarly secured to the baseplate 25.

Above the lower jaws 26 and 27, and the radius comer 16, is located an upright plate structure 35 (as shown in the figures) which serves to support the jaws 29 and 30 and the lever arm 31 of the upper clamping means 14 in a manner similar to that of the lower clamping structure 12.

The clamping assemblies 12 and 14 serve to grip or clamp a test sample (not shown) in a manner which prevents it from slipping in the jaws when it is bent and stretched in the manner explained hereinafter. As such, the clamping structures 12 and 14 are given by way of example only. Any clamping means capable of securing a test sample in such a manner may be used, and pneumatic or hydraulic actuating means may be employed to actuate the clamping jaws.

The radius comer 16, as best seen in FIG. 1, is removably secured to the support block 33 by suitable bolts 35a (only one of which is shown), and positioned in substantial vertical alignment with the clamping jaws 26, 27, 29, and 30.

The cam plates 18 and 20 are removably secured to the baseplate 25 by bolts extending horizontally through the plates and into supporting plates 36 and 38 respectively. The supporting plates are suitably attached to the baseplate 25, for example, by welding as shown in FIG. 2.

Above the radius corner 16, and beneath the upper clamping jaws 29 and 30, is disposed a flat plate 40 suitably attached to the lower edge of the plate 35 as best seen in FIG. I. The plate 40 has a door 41 vertically hinged at one side thereof so that the door can swing away from the plate 40 on the vertical axis of the hinge.

The upper clamping assembly 14 is made movable about the radius corner means 16 by virtue of two rollers 42 and 44, suitably attached to the upright plate 35, as best seen in FIG. 2, and disposed in respective rolling engagement with the cam surfaces 22 and 24. To translate the upper clamping assembly about the radius comer, the upright plate 35 is attached to two vertical, parallel bars 45 pivoted at their lower ends by suitably mounted bolts 46 extending through support blocks 47 (receiving the lower ends of the bars) and into the support plates 36 and 38. As shown in the figures, the bars may extend directly through the upright plate 35, and be welded thereto at the upper and lower edges thereof. The lower end of each bar is provided with an enlarged cap or flange 49 which retains a coiled spring 50 between the cap and the pivot block 47.

The device 10, as thus far described, functions to simulate the bending and stretching conditions and forces encountered by materials in forming operations involving a substantial bend and a substantial amount of stretch or elongation. This is accomplished by tightly clamping portions of a sample of the material (not shown) between the jaws of the clamping assemblies I2 and 14, and translating the assembly 14 about the radius corner 16 along the surfaces 22 and 24 of the cam plates 18 and 20. The radius corner 16 is thus chosen to represent or simulate the radius of the bend encountered in the forming operation, and the cam structures 18 and 20 are chosen to provide a representative amount of stretch. The stretch is provided by a constant radius on the cam plates along the cam surfaces, the center of curvature of which is disposed a known, predetermined distance from the center of the bend radius 16. (The effect produced is similar to that produced by a cam with an increasing radius). The amount of stretch imposed is governed by the distance of the center of curvature of the cam plates from the center of the bend radius. Thus, for small changes in stretch the position of the radius 16 may be moved. For larger changes new cam plates may be substituted.

After the desired radius corner 16 and cam structures 18 and 20 are chosen and secured to the baseplate 25, as described above, the device is operated in the following manner.

The movable clamping assembly 14 is positioned in the upright manner shown in the figures. The clamping jaws 26 and 30 are disposed in their relaxed position, and the door 41 is swung away from the plate 40. A sample of the material to be tested is then disposed against the inner surface of the plate 40, and two opposed ends of the sample are disposed between the jaws of the clamping assemblies 12 and 14 respectively. The door 41 is then closed on the sample to ensure that the sample is substantially straight or flat before the sample is finally tightly clamped by the jaws of the clamping assemblies.

With the door 41 shut on the sample, and the jaws 26 to 29 tightly clamping the sample, the sample is pulled over the radius comer 16 by applying a force to the bars 45 in a manner which moves the clamping assembly 14 about the radius comer. This movement is permitted by the pivoting action of the bars 45 at the bolts 46, and the rolling action of the rollers 42 and 44 on the cam surfaces 22 and 24 respectively in a cam-following manner. As the clamping assembly 14 follows along the cam surfaces, the sample is both bent and elongated in amounts at least as great as that encountered in the forming operation simulated by the corner 16 and the cam structures 22 and 24. The springs 50 (at the lower ends of the bars 45) allow the bars to move in a radially outward direction as the distance between radius corner 16 and clamp assembly 14, and between the two clamp assemblies 12 and 14, increases.

If the above sample is a coated material, for example, a painted aluminum strip, the paint, particularly at the bend, can be visually (or otherwise) examined after the bending and stretching operation to determine the integrity of the paint or coating. If the paint has cracked or otherwise deteriorated, the batch from which the sample was taken can be rejected for an equivalent forming operation. In this manner, control of the quality of such painted or coated material is quickly and economically provided.

The invention, however, is not limited to testing only the integrity of coating surfaces. The device 10 can be used to test for the occurrence of undesirable surface conditions that result from bending and elongation of materials. For example, when a strip of metal is formed such that the forces are in a direction other than the direction in which the metal was rolled, there is a tendency of the grains of the metal to open which produces a surface texture resembling the strands of a rope or sinew. By orienting the grain structure with respect to the radius comer 16, the effect of forming forces on the sample can be simulated. If it is desirable that the area of the bend be substantially smooth and free of such a surface condition, a sample of the aluminum can be tested by the device 10 before the bulk of the aluminum is formed in an operation simulated by the device. Again, in this manner, quality control of the formed material is easily and efficiently provided.

It should now be apparent from the foregoing description that a new and useful device has been disclosed for simulating the degree of bend and the amount of elongation or stretch encountered by a fonnable material in a forming operation. The device comprises basically two clamping means spaced about a radius corner with one clamping means movably positioned to follow cam surfaces having radii which effectively increase from the center of the radius comer in the direction of movement of the clamping means. By having the radius comer and cam surfaces removably attached to a base structure, a variety of forming conditions can be simulated by the single device of the invention.

Though the invention has been described with a certain degree of particularity, changes can be made therein without departing from the spirit and scope thereof.

Having thus described my invention and certain embodiments thereof, 1 claim:

1. A device for testing the effect of forming forces on the surface condition of a formable material by bending and stretching the material, said device comprising means for clamping the material at two spaced-apart locations,

a radius comer means disposed in a fixed location between the locations of said clamping means, and in substantial alignment therewith,

curved cam means of predetermined, increasing radius about said corner means, and

means for moving at least one of said clamping means along said cam means of increasing radius about said corner means, the increasing radius increasing the distance between said clamps,

the movement of said one clamping means being operative to bend and stretch the material over said corner means with a severity of bend and an amount of elongation simulating that encountered in a forming operation which bends and stretches the material in substantial amounts.

2. The device of claim 1 in which the means for moving the one clamping means in an increasing radius includes two structures providing two cam surfaces respectively located on each side of an in fixed relationship to the radius corner means, and

cam-following means attached to the movable clamping means on each side thereof, said cam-following means being disposed to engage said cam surfaces.

3. The device of claim 1 in which the means for moving the one clamping means in an increasing radius about the corner means includes two plate structures providing two cam surfaces having a center of curvature disposed a predetermined distance from the center of the radius corner means, the cam surfaces of said plate structures having a constant radius about their center of curvature.

4. The device of claim 1 including a structure for straightening the formable material before it is bent and elongated, said means being disposed between the locations of the clamping means, and in substantial alignment therewith.

5. A method of testing the effect of forming forces on the surface condition of a formable material by bending and stretching the material, said method comprising the steps of disposing the material adjacent to a radius comer means,

clamping portions of the material at spaced apart locations on opposite sides of said corner means, and

increasing the distance between the clamped portions of the material by moving at least one of said clamped portions of the material in a curve of predetermined, increasing radius about the corner means,

the movement of the material being effective to bend and stretch the material with a severity of bend and an amount of elongation simulating that encountered in a forming operation which bends and stretches the material in substantial amounts.

6. The method of claim 5 including the step of straightening the material before it is clamped at at least one of the clamping locations. 

1. A device for testing the effect of forming forces on the surface condition of a formable material by bending and stretching the material, said device comprising means for clamping the material at two spaced-apart locations, a radius corner means disposed in a fixed location between the locations of said clamping means, and in substantial alignment therewith, curved cam means of predetermined, increasing radius about said corner means, and means for moving at least one of said clamping means along said cam means of increasing radius about said corner means, the increasing radius increasing the distance between said clamps, the movement of said one clamping means being operative to bend and stretch the material over said corner means with a severity of bend and an amount of elongation simulating that encountered in a forming operation which bends and stretches the material in substantial amounts.
 2. The device of claim 1 in which the means for moving the one clamping means in an increasing radius includes two structures providing two cam surfaces respectively located on each side of an in fixed relationship to the radius corner means, and cam-following means attached to the movable clamping means on each side thereof, said cam-following means being disposed to engage said cam surfaces.
 3. The device of claim 1 in which the means for moving the one clamping means in an increasing radius about the corner means includes two plate structures providing two cam surfaces having a center of curvature disposed a predetermined distance from the center of the radius corner means, the cam surfaces of said plate structures having a constant radius about their center of curvature.
 4. The device of claim 1 including a structure for straightening the formable material before it is bent and elongated, said means being disposed between the locations of the clamping means, and in substantial alignment therewith.
 5. A method of testing the effect of forming forces on the surface condition of a formable material by bending and stretching the material, said method comprising the steps of disposing the material adjacent to a radius corner means, clamping portions of the material at spaced apart locations on opposite sides of said corner means, and increasing the distance between the clamped portions of the material by moving at least one of said clamped portions of the material in a curve of predetermined, increasing radius about the corner means, the movement of the material being effective to bend and stretch the material with a severity of bend and an amount of elongation simulating that encountered in a forming operAtion which bends and stretches the material in substantial amounts.
 6. The method of claim 5 including the step of straightening the material before it is clamped at at least one of the clamping locations. 